U.S. patent application number 12/570462 was filed with the patent office on 2011-03-31 for shielded differential inductor.
This patent application is currently assigned to SILICON LABORATORIES INC.. Invention is credited to Mustafa H. Koroglu, Alessandro Piovaccari, Ramin Poorfard, Sherry X. Wu.
Application Number | 20110076979 12/570462 |
Document ID | / |
Family ID | 43780932 |
Filed Date | 2011-03-31 |
United States Patent
Application |
20110076979 |
Kind Code |
A1 |
Wu; Sherry X. ; et
al. |
March 31, 2011 |
SHIELDED DIFFERENTIAL INDUCTOR
Abstract
A shielded differential inductor forms a high quality factor
(high-Q) inductor that is configured to attenuate frequency spurs
and/or noise from magnetic coupling generated by electrical
structures on or off of a substrate as well as interference
received by other components from magnetic coupling generated by
the inductor. The shielded differential inductor includes a
differential inductor and a shield that substantially isolates the
electrical field between the inductor and the substrate to reduce
substrate current loss. The shield includes sets of finger
structures that extend beyond the width of the inductor and a hub
and spoke configuration of ground conductors that connect the sets
of finger structures to ground.
Inventors: |
Wu; Sherry X.; (Austin,
TX) ; Koroglu; Mustafa H.; (Austin, TX) ;
Poorfard; Ramin; (Austin, TX) ; Piovaccari;
Alessandro; (Austin, TX) |
Assignee: |
SILICON LABORATORIES INC.
Austin
TX
|
Family ID: |
43780932 |
Appl. No.: |
12/570462 |
Filed: |
September 30, 2009 |
Current U.S.
Class: |
455/318 ;
331/117FE; 336/192; 336/200; 336/225; 336/84R |
Current CPC
Class: |
H01F 17/0006 20130101;
H01F 2017/008 20130101; H03B 5/1228 20130101; H01L 23/5227
20130101; H01L 23/5225 20130101; H03B 5/1212 20130101; H03B 5/124
20130101 |
Class at
Publication: |
455/318 ;
336/84.R; 331/117.FE; 336/192; 336/200; 336/225 |
International
Class: |
H04B 1/16 20060101
H04B001/16; H01F 27/36 20060101 H01F027/36; H03B 5/12 20060101
H03B005/12 |
Claims
1. An apparatus formed on a substrate, the apparatus comprising: an
inductor; and a shield including a first set of finger structures
formed in proximity to a first portion of the inductor and a ground
connection connected to the first set of finger structures, each of
the finger structures in the first set extending beyond a width of
the first portion of the inductor in a first direction that is
orthogonal to a second direction of current flow in the first
portion of the inductor.
2. The apparatus of claim 1 wherein the inductor includes a
differential inductor with first and second conductive loops
coupled in series.
3. The apparatus of claim 2 wherein the first and the second
conductive loops are configured such that a first magnetic field of
the first conductive loop at least partially cancels a second
magnetic field of the second conductive loop.
4. The apparatus of claim 2 wherein the first conductive loop
includes the first portion, and wherein the ground connection
includes a first connector that connects to each of the first set
of finger structures and a first conductor that connects to the
first connector and extends to a center point of the first
conductive loop.
5. The apparatus of claim 4 wherein the shield includes a second
set of finger structures formed in proximity to a second portion of
the inductor and connected to the ground connection, wherein each
of the finger structures in the second set extending beyond a width
of the second portion of the inductor in a third direction that is
orthogonal to a fourth direction of current flow in the second
portion of the inductor, and wherein the third direction differs
from the first direction.
6. The apparatus of claim 5 wherein the first conductive loop
includes the second portion, and wherein the ground connection
includes a second connector that connects to each of the second set
of finger structures and a second conductor that connects to the
second connector and extends to the center point of the first
conductive loop.
7. The apparatus of claim 6 wherein the shield includes a third set
of finger structures formed in proximity to a third portion of the
inductor and connected to the ground connection, wherein each of
the finger structures in the third set extending beyond a width of
the third portion of the inductor in a fifth direction that is
orthogonal to a sixth direction of current flow in the second
portion of the inductor, wherein the second conductive loop
includes the third portion, and wherein the ground connection
includes a third connector that connects to each of the third set
of finger structures and a third conductor that connects to the
third connector and extends to a center point of the second
conductive loop.
8. The apparatus of claim 5 wherein the second conductive loop
includes the second portion, and wherein the ground connection
includes a second connector that connects to each of the second set
of finger structures and a second conductor that connects to the
second connector and extends to a center point of the second
conductive loop.
9. The apparatus of claim 1 further comprising: core circuitry
symmetrically positioned with respect to a point of the inductor
where a minimum voltage swing of the inductor occurs.
10. The apparatus of claim 1 further comprising: a substrate;
wherein the inductor and the shield are formed on the substrate,
and wherein an area underneath the inductor on the substrate
comprises raw substrate.
11. A controlled oscillator formed on a substrate, the controlled
oscillator comprising: an amplifier; a varactor; and a differential
inductor coupled in parallel with the amplifier and varactor and
having a shield that includes a plurality of sets of finger
structures each connected to a ground connection, and wherein each
of the plurality of sets of finger structures is formed in
proximity to a different portion of the inductor such that the
finger structures of each set extend beyond a width of the inductor
in a direction that is orthogonal to the direction of current flow
in the corresponding portion of the inductor.
12. The controlled oscillator of claim 11 wherein the differential
inductor includes first and second conductive loops coupled in
series.
13. The controlled oscillator of claim 12 wherein the first and the
second conductive loops are configured such that a first magnetic
field of the first conductive loop at least partially cancels a
second magnetic field of the second conductive loop.
14. The controlled oscillator of claim 12 wherein the ground
connection includes a first hub, a first plurality of spokes that
connect the first hub to a first subset of the plurality of sets of
finger structures formed in proximity to the first conductive loop,
a second hub, and a second plurality of spokes that connect the
second hub to a second subset of the plurality of sets of finger
structures formed in proximity to the second conductive loop.
15. The controlled oscillator of claim 11 wherein the varactor is
symmetrically formed with respect to the differential inductor.
16. A media system comprising: a communications device configured
to receive an analog input signal and generate an output signal,
the communications device includes: a controlled oscillator
including a differential inductor coupled in parallel with an
amplifier and a varactor and having a shield that includes a
plurality of sets of finger structures each connected to a ground
connection, each of the plurality of sets of finger structures is
formed in proximity to a different portion of the inductor such
that the finger structures of each set extend beyond a width of the
inductor in a direction that is orthogonal to the direction of
current flow in the corresponding portion of the inductor, and the
controlled oscillator configured to generate a mixing signal using
the differential inductor; a mixer configured to generate an analog
baseband signal from the analog input signal and the mixing signal;
intermediate frequency (IF) filter circuitry configured to convert
the analog baseband signal to a digital baseband signal; and
processing circuitry configured to generate the output signal
responsive to the digital baseband signal from the IF filter
circuitry; a processing unit configured to generate a media signal
in response to the output signal from the communications
device.
17. The media system of claim 16 further comprising: a media output
device configured to generate a media output in response to the
media signal from the processing circuitry.
18. The media system of claim 17 further comprising: an
input/output unit configured to provide a control signal to the
media output device.
19. The media system of claim 16 wherein the differential inductor
includes first and second conductive loops coupled in series.
20. The media system of claim 19 wherein the first and the second
conductive loops are configured such that a first magnetic field of
the first conductive loop at least partially cancels a second
magnetic field of the second conductive loop.
Description
BACKGROUND
[0001] Analog and mixed signal integrated circuits may include
passive components such as capacitors and inductors that are formed
on a semiconductor substrate. In operation, these components may
produce or receive interference that may cause undesired behavior
on other components on the substrate. The received interference may
originate in components on the substrate or components in proximity
to the substrate (e.g., bond wires or circuitry on a printed
circuit board). In some instances, the interference may transfer to
the other components through magnetic coupling or across the
substrate and may take the form of frequency spurs or noise. For
example, a component on the substrate may generate a mutual
inductance with another component on or off of the substrate that
produces an induced voltage that may take the form of a spur or
noise. The induced voltage may be proportional to the amount of
interference and the mutual inductance. Circuitry on the substrate,
therefore, may be designed to minimize the effects of the mutual
inductance between a component on the substrate and a component on
or off of the substrate.
SUMMARY
[0002] According to one exemplary embodiment, an apparatus formed
on a substrate is provided. The apparatus includes an inductor and
a shield including a first set of finger structures formed in
proximity to a first portion of the inductor and a ground
connection connected to the first set of finger structures. Each of
the finger structures in the first set extends beyond a width of
the first portion of the inductor in a first direction that is
orthogonal to a second direction of current flow in the first
portion of the inductor.
[0003] According to another exemplary embodiment, a controlled
oscillator formed on a substrate is provided. The controlled
oscillator includes an amplifier, a varactor, and a differential
inductor coupled in parallel with the amplifier and varactor. The
differential inductor has a shield that includes a plurality of
sets of finger structures each connected to a ground connection.
Each of the plurality of sets of finger structures is formed in
proximity to a different portion of the inductor such that the
finger structures of each set extend beyond a width of the inductor
in a direction that is orthogonal to the direction of current flow
in the corresponding portion of the inductor.
[0004] According to a further exemplary embodiment, a media system
is provided. The media system includes a communications device
configured to receive an analog input signal and generate an output
signal and a processing unit configured to generate a media signal
in response to the output signal from the communications device.
The communications device includes a controlled oscillator, a
mixer, intermediate frequency (IF) filter circuitry, and processing
circuitry. The controlled oscillator includes a differential
inductor coupled in parallel with an amplifier and a varactor. The
differential inductor has a shield that includes a plurality of
sets of finger structures each connected to a ground connection.
Each of the plurality of sets of finger structures is formed in
proximity to a different portion of the inductor such that the
finger structures of each set extend beyond a width of the inductor
in a direction that is orthogonal to the direction of current flow
in the corresponding portion of the inductor. The controlled
oscillator configured to generate a mixing signal using the
differential inductor. The mixer is configured to generate an
analog baseband signal from the analog input signal and the mixing
signal. The IF filter circuitry is configured to convert the analog
baseband signal to a digital baseband signal, and the processing
circuitry configured to generate the output signal responsive to
the digital baseband signal from the IF filter circuitry.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIGS. 1A-1E are diagrams illustrating one embodiment of a
shielded differential inductor.
[0006] FIGS. 2A-2E are diagrams illustrating another embodiment of
a shielded differential inductor.
[0007] FIGS. 3A-3D are diagrams illustrating embodiments of shields
for differential inductors.
[0008] FIG. 4 is a circuit diagram illustrating one embodiment of a
controlled oscillator.
[0009] FIG. 5 is a block diagram illustrating one embodiment of
selected portions of a communications device.
[0010] FIG. 6 is a block diagram illustrating one embodiment of a
media system that includes a communications device.
DETAILED DESCRIPTION
[0011] In the following Detailed Description, reference is made to
the accompanying drawings, which form a part hereof, and in which
is shown by way of illustration specific embodiments in which the
invention may be practiced. In this regard, directional
terminology, such as "top," "bottom," "front," "back," "leading,"
"trailing," etc., is used with reference to the orientation of the
Figure(s) being described. Because components of embodiments of the
present invention can be positioned in a number of different
orientations, the directional terminology is used for purposes of
illustration and is in no way limiting. It is to be understood that
other embodiments may be utilized and structural or logical changes
may be made without departing from the scope of the present
invention. The following detailed description, therefore, is not to
be taken in a limiting sense, and the scope of the present
invention is defined by the appended claims.
[0012] As described herein, a shielded differential inductor forms
a high quality factor (high-Q) inductor that is configured to
attenuate frequency spurs and/or noise from magnetic coupling
generated by electrical structures on or off of a substrate as well
as interference received by other components from magnetic coupling
generated by the inductor. The shielded differential inductor
includes a differential inductor and a shield that substantially
isolates the electrical field between the inductor and the
substrate to reduce substrate current loss. The shield includes
sets of finger structures that extend beyond the width of the
inductor and a hub and spoke configuration of ground conductors
that connect the sets of finger structures to ground. Core
circuitry that may combine with the inductor to form a controlled
oscillator may be symmetrically placed relative to the inductor to
minimize current loss and improve the Q of the inductor.
[0013] FIG. 1A is a bottom view diagram illustrating an embodiment
of a shielded differential inductor 100 in an x-y plane 101.
Shielded differential inductor 100 includes a differential inductor
102 and a shield 112 formed in proximity to differential inductor
102.
[0014] Differential inductor 102 includes a pair of conductive
loops 102A and 102B. Loop 102A includes a terminal 104, and loop
102B includes a terminal 106. Loops 102A and 102B are arranged
substantially in the shape of a figure eight in x-y plane 101. The
figure eight shape of loops 102A and 102B includes a disconnected
or electrically open region between terminals 104 and 106 and a
conductive connection 108 between loops 102A and 102B. In the
embodiment of FIG. 1A, each loop 102A and 102B forms a
substantially octagonal shape that is symmetric in the x and y
directions of x-y plane 101. In other embodiments, each loop 102A
and 102B may form other substantially polygonal and/or rounded
(e.g., circular) shapes with or without symmetry in the x and/or y
directions of x-y plane 101. Loops 102A and 102B are configured
such that a magnetic field of loop 102A at least partially cancels
a magnetic field of loop 102B. The magnetic fields of loops 102A
and 102B may be generated by loops 102A and 102B, respectively, or
received by loops 102A and 102B, respectively.
[0015] Shield 112 includes sets of conductive finger structures 114
connected to a ground conductor 116 via respective conductive
connectors 118. Each set of figure structures 114 includes any
suitable number of elongated finger structures that are formed to
be substantially parallel to one another in x-y plane 101. Each set
of finger structures 114 is also formed in proximity to a
respective portion of inductor 102 such that the finger structures
of each respective set are configured in a direction that is
substantially orthogonal to the direction of the current flow in
the respective portion of inductor 102. Each finger structure
extends beyond each edge of a respective portion of inductor 102 in
x-y plane 101 (i.e., beyond the width of inductor 102) such that a
length of each finger (l.sub.FIN) is greater than a width
(w.sub.IND) of the respective portion of inductor 102 in x-y plane
101. Each finger structure of each set connects to a respective
connector 118 which in turn connects to ground conductor 116.
[0016] Ground conductor 116 includes elongated portions that form
spokes 120 that connect to connectors 118. Each spoke 120 extends
in a direction that is parallel to the direction of the respective
set of finger structures 114. The respective sets of spokes 120 of
loops 102A and 102B converge and connect at respective hubs that
are at or near respective center points of loops 102A and 102B in
the x-y plane. Ground conductor 116 also includes a conductor 122
that connects the set of spokes 120 of loop 102A with the set of
spokes of loop 102B.
[0017] Each connector 118 connects only to a corresponding set of
finger structures 114 and a corresponding spoke 120. Each connector
118 extends in a direction that is orthogonal to the direction of a
corresponding set of finger structures 114 and a corresponding
spoke 120 in x-y plane 101. Each connector 118 does not extend
substantially beyond the outer finger structures of a corresponding
set of finger structures 114 in x-y plane 101 such that adjacent
connectors 118 of adjacent sets of finger structures 114 do not
directly connect to one another (i.e., connectors 118 are separated
from one another).
[0018] As shown in FIG. 1B, loops 102A and 102B each form inductive
loops that are coupled in series and generate electrical current
that flows in opposite directions. For example, loop 102A may
generate current I.sub.A that flows in a clockwise direction and
loop 102B may generate current I.sub.B that flows in a
counterclockwise direction as shown. Because the currents of loops
102A and 102B flow in opposite directions, the magnetic fields
generated or received by loops 102A and 102B at least partially
cancel one another.
[0019] Inductor 102 and shield 112 may be formed in any suitable
number of layers of material on a semiconductor substrate 130 using
any suitable semiconductor manufacturing process as shown in FIG.
1C. As shown in FIG. 1C, the layers that form shield 112 and
inductor 130 are formed on a substrate 130 as indicated by the z
direction 131. Although not shown in FIG. 1C, any number of layers
may be formed between substrate 130 the layers that form shield 112
and inductor 102.
[0020] In one embodiment, ground conductor 116 and connector 118
may be formed in one or more conductive metal layers, finger
structures 114 may be formed in one or more conductive polysilicon
layers, and inductor 102 may be formed in one or more conductive
metal layers. In other embodiments, ground conductor 116, connector
118, finger structures 114, and inductor 102 may be formed in other
suitable types and/or numbers of conductive layers.
[0021] In other embodiments, the layers that include ground
conductor 116 and finger structures 114 may be swapped such that
ground conductor 116 is formed in a layer between the layer that
includes connectors 118 and the layer that includes inductor 102
and finger structures 114 are formed in a layer between substrate
130 and the layer that includes connectors 118.
[0022] Shielded differential inductor 100 forms a high quality
factor (high-Q) inductor that is configured to attenuate frequency
spurs and/or noise from magnetic coupling generated by electrical
structures on or off of substrate 130. Shielded differential
inductor 100 is also configured to attenuate interference (e.g.,
frequency spurs and/or noise) received by other components from
magnetic coupling generated by inductor 102. By extending the
finger structures of shield 112 beyond the width of inductor 102,
the sets of finger structures 114 substantially isolate the
electrical field between inductor 102 and substrate 130 and reduce
substrate current loss. In addition, the finger structures minimize
eddy current loss compared to a solid shield to improve the Q of
inductor 102.
[0023] The extended finger structures may also allow the size of
inductor 102 to be changed without changing the size of shield 112.
For example, if a larger or smaller inductor 102 becomes desirable,
the size of inductor 102 may be increased or decreased within a
range relative to the size of shield 112 and retain the benefits
provided by the finger structures extending beyond the width of
inductor 102. With a change in size of inductor 102, the finger
structures may extend beyond opposing sides of inductor 102 by
different lengths. Even with these different lengths, the finger
structures continue to substantially isolate the electrical field
between inductor 102 and substrate 130 and reduce substrate current
loss. Accordingly, size of inductor 102 may be adjusted in a
straightforward and cost effective manner.
[0024] FIG. 1D illustrates a portion of a circuit equivalent of the
shielded differential inductor 100. Each finger structure in a set
of figure structures 114 effectively forms a capacitance C between
a respective portion of inductor 102 and ground conductor 116 via a
respective spoke 120. The hub and spoke distribution of the figure
structures in shield 112 along with the separation between
connectors 118 (shown in FIG. 1A) may prevent a current loop from
forming in shield 112 to further minimize the current loss in
shield 112.
[0025] In one embodiment shown in FIG. 1E, shielded differential
inductor 100 may form a portion of a controlled oscillator (shown
in FIG. 4 and described in additional detail below) along with a
core circuitry 140 and connecting bars 142 and 144. As shown in
FIG. 4, core circuitry 140 may be formed in proximity to inductor
102 and may include a varactor 284, a resistor 286 that represents
the lossy component from inductor 100, varactor 284, etc., and an
amplifier 288 coupled in parallel with differential inductor
100.
[0026] Core circuitry 140 may be symmetrically located under the
crossover region and along the y-axis of inductor 102 to minimize
the magnetic coupling and Q degradation of inductor 102 caused by
the metallization effect of core circuitry 140. Because inductor
102 is a differential inductor, the minimum voltage swing of
inductor 102 occurs at a symmetry point of inductor 102 in the x
and y-axes. Core circuitry 140 may be symmetrically placed with
respect to this symmetry point to minimize the capacitive coupling
between core circuitry 140 and inductor 102. This placement of core
circuitry 140 also minimizes the routing distance between inductor
102 and varactor 284 to minimize the loss between inductor 102 and
varactor 284 and increase the quality factor of the LC tank formed
by inductor 102 and varactor 284. Connecting bars 142 and 144 are
configured to provide good conductivity between inductor 102 and
core circuitry 140 to reduce current loss on connecting bars 142
and 144 as well as eddy current loss caused by connecting bars 142
and 144. This placement of core circuitry 140 further minimizes
electric coupling between the crossover section of inductor 102 and
core circuitry 140 because of the minimum signal swing at the
crossover point of differential inductor 102.
[0027] In addition, varactor 284 of core circuitry 140 may be
divided into sections to provide a symmetric layout of core
circuitry 140. As a result, impacts from core circuitry 140 on
inductor 102 may be differentially symmetric.
[0028] The area of substrate 130 underneath inductor 102 may be
configured to include as much raw substrate (i.e., neither PWell or
NWell) as possible via a free process mask. A portion underneath
core circuitry 140 may include areas of PWell or NWell, but the
remaining area of substrate 130 underneath inductor 102 includes
raw substrate. By doing so, the resistivity of substrate 130 is
increased to result in a decrease of any induced substrate current
and an increase of the quality factor of the LC tank formed by
inductor 102 and varactor 284.
[0029] FIG. 2A is a bottom view diagram illustrating another
embodiment of a shielded differential inductor 200 in an x-y plane
201. Shielded differential inductor 200 includes a differential
inductor 202 and a shield 212 formed in proximity to differential
inductor 202.
[0030] Differential inductor 202 includes a pair of conductive
loops 202A and 202B. Loop 202A includes a terminal 204, and loop
202B includes a terminal 206. Loops 202A and 202B are arranged
substantially in the shape of an extended figure eight in x-y plane
101. The extended figure eight shape of loops 202A and 202B
includes a disconnected or electrically open region between
terminals 204 and 206 and a conductive connection 208 between loops
202A and 202B. In the embodiment of FIG. 2A, each loop 202A and
202B forms a substantially octagonal shape that is symmetric in the
x and y directions of x-y plane 201. In other embodiments, each
loop 202A and 202B may form other substantially polygonal and/or
rounded (e.g., circular) shapes with or without symmetry in the x
and/or y directions of x-y plane 201. Loops 202A and 202B are
configured such that a magnetic field of loop 202A at least
partially cancels a magnetic field of loop 202B. The magnetic
fields of loops 202A and 202B may be generated by loops 102A and
202B, respectively, or received by loops 202A and 202B,
respectively.
[0031] Shield 212 includes sets of conductive finger structures 214
connected to a ground conductor 216 via respective conductive
connectors 218. Each set of figure structures 214 includes any
suitable number of elongated finger structures that are formed to
be substantially parallel to one another in x-y plane 201. Each set
of finger structures 214 is also formed in proximity to a
respective portion of inductor 202 such that the finger structures
of each respective set are configured in a direction that is
substantially orthogonal to the direction of the current flow in
the respective portion of inductor 202. Each finger structure
extends beyond each edge of a respective portion of inductor 202 in
x-y plane 201 (i.e., beyond the width of inductor 202) such that a
length of each finger (l.sub.FIN) is greater than a width
(w.sub.IND) of the respective portion of inductor 202 in x-y plane
201. Each finger structure of each set connects to a respective
connector 218 which in turn connects to ground conductor 216.
[0032] Ground conductor 216 includes elongated portions that form
spokes 220 that connect to connectors 218. Each spoke 220 extends
in a direction that is parallel to the direction of the respective
set of finger structures 214. The respective sets of spokes 220 of
loops 202A and 202B converge and connect at respective hubs that
are at or near respective center points of loops 202A and 202B in
the x-y plane. Ground conductor 216 also includes a conductor 222
that connects the set of spokes 220 of loop 202A with the set of
spokes of loop 202B.
[0033] Each connector 218 connects only to a corresponding set of
finger structures 214 and a corresponding spoke 220. Each connector
218 extends in a direction that is orthogonal to the direction of a
corresponding set of finger structures 214 and a corresponding
spoke 220 in x-y plane 201. Each connector 218 does not extend
substantially beyond the outer finger structures of a corresponding
set of finger structures 214 in x-y plane 101 such that adjacent
connectors 218 of adjacent sets of finger structures 214 do not
directly connect to one another (i.e., connectors 218 are separated
from one another).
[0034] As shown in FIG. 2B, loops 202A and 202B each form inductive
loops that are coupled in series and generate electrical current
that flows in opposite directions. For example, loop 202A may
generate current I.sub.A that flows in a clockwise direction and
loop 202B may generate current I.sub.B that flows in a
counterclockwise direction as shown. Because the currents of loops
202A and 202B flow in opposite directions, the magnetic fields
generated or received by loops 202A and 202B at least partially
cancel one another.
[0035] Inductor 202 and shield 212 may be formed in any suitable
number of layers of material on a semiconductor substrate 130 using
any suitable semiconductor manufacturing process as shown in FIG.
2C. As shown in FIG. 2C, the layers that form shield 212 and
inductor 230 are formed on a substrate 230 as indicated by the z
direction 231. Although not shown in FIG. 2C, any number of layers
may be formed between substrate 230 the layers that form shield 212
and inductor 202.
[0036] In one embodiment, ground conductor 216 and connector 218
may be formed in one or more conductive metal layers, finger
structures 214 may be formed in one or more conductive polysilicon
layers, and inductor 202 may be formed in one or more conductive
metal layers. In other embodiments, ground conductor 216, connector
218, finger structures 214, and inductor 202 may be formed in other
suitable types and/or numbers of conductive layers.
[0037] In other embodiments, the layers that include ground
conductor 216 and finger structures 214 may be swapped such that
ground conductor 216 is formed in a layer between the layer that
includes connectors 218 and the layer that includes inductor 202
and finger structures 214 are formed in a layer between substrate
230 and the layer that includes connectors 218.
[0038] Shielded differential inductor 200 forms a high quality
factor (high-Q) inductor that is configured to attenuate frequency
spurs and/or noise from magnetic coupling generated by electrical
structures on or off of substrate 230. Shielded differential
inductor 200 is also configured to attenuate interference (e.g.,
frequency spurs and/or noise) received by other components from
magnetic coupling generated by inductor 202. By extending the
finger structures of shield 212 beyond the width of inductor 202,
the sets of finger structures 214 substantially isolate the
electrical field between inductor 202 and substrate 230 and reduce
substrate current loss. In addition, the finger structures minimize
eddy current loss compared to a solid shield to improve the Q of
inductor 202.
[0039] The extended figure structures may also allow the size of
inductor 202 to be changed without changing the size of shield 212.
For example, if a larger or smaller inductor 202 becomes desirable,
the size of inductor 202 may be increased or decreased within a
range relative to the size of shield 112 and retain the benefits
provided by the finger structures extending beyond the width of
inductor 202. With a change in size of inductor 202, the finger
structures may extend beyond opposing sides of inductor 202 by
different lengths. Even with these different lengths, the finger
structures continue to substantially isolate the electrical field
between inductor 202 and substrate 230 and reduce substrate current
loss. Accordingly, size of inductor 202 may be adjusted in a
straightforward and cost effective manner.
[0040] FIG. 2D illustrates a portion of a circuit equivalent of the
shielded differential inductor 200. Each finger structure in a set
of figure structures 214 effectively forms a capacitance C between
a respective portion of inductor 202 and ground conductor 216 via a
respective spoke 220. The hub and spoke distribution of the figure
structures in shield 212 along with the separation between
connectors 218 (shown in FIG. 2A) may prevent a current loop from
forming in shield 212 to further minimize the current loss in
shield 212.
[0041] In one embodiment shown in FIG. 2E, shielded differential
inductor 200 may form a portion of a controlled oscillator (shown
in FIG. 4 and described in additional detail below) along with a
core circuitry 240 and connecting bars 242 and 244. As shown in
FIG. 4, core circuitry 240 may be formed in proximity to inductor
102 and may include varactor 284, resistor 286, and amplifier 288
coupled in parallel with differential inductor 200.
[0042] Core circuitry 240 may be symmetrically located under the
cross over region and along the y-axis of inductor 202 to minimize
the magnetic coupling and Q degradation of inductor 202 caused by
the metallization effect of core circuitry 240. Because inductor
202 is a differential inductor, the minimum voltage swing of
inductor 202 occurs at a symmetry point of inductor 202 in the x
and y-axes. Core circuitry 240 may be symmetrically placed with
respect to this symmetry point to minimize the capacitive coupling
between core circuitry 240 and inductor 202. This placement of core
circuitry 240 also minimizes the routing distance between inductor
202 and varactor 284 to minimize the loss between inductor 202 and
varactor 284 and increase the quality factor of the LC tank formed
by inductor 202 and varactor 284. Connecting bars 242 and 244 are
configured to provide good conductivity between inductor 202 and
core circuitry 240 to reduce current loss on connecting bars 242
and 244 as well as eddy current loss caused by connecting bars 242
and 244. This placement of core circuitry 240 further minimizes
electric coupling between the crossover section of inductor 202 and
core circuitry 240 because of the minimum signal swing at the
crossover point of differential inductor 202.
[0043] In addition, varactor 284 of core circuitry 240 may be
divided into sections to provide a symmetric layout of core
circuitry 240. As a result, impacts from core circuitry 240 on
inductor 202 may be differentially symmetric.
[0044] The area of substrate 230 underneath inductor 202 may be
configured to include as much raw substrate (i.e., neither PWell or
NWell) as possible via a free process mask. A portion underneath
core circuitry 240 may include areas of PWell or NWell, but the
remaining area of substrate 230 underneath inductor 202 includes
raw substrate. By doing so, the resistivity of substrate 230 is
increased to result in a decrease of any induced substrate current
and an increase of the quality factor of the LC tank formed by
inductor 202 and varactor 284. FIGS. 3A-3D are diagrams
illustrating various embodiments of ground paths for shields for
differential inductors. FIGS. 3A and 3B illustrate the ground paths
for shields 112 and 212 for differential inductors 102 and 202,
respectively. The ground path for differential inductor 102
includes ground conductor 116 and connectors 118, and the ground
path for differential inductor 202 includes ground conductor 216
and connectors 218.
[0045] As illustrated by the embodiments of ground paths 252 and
262 in FIGS. 3C and 3D, respectively, various alterations of the
ground paths of the embodiments of FIGS. 3A and 3B may be made
while maintaining the potential advantages described above. In FIG.
3C, for example, ground path 252 replaces the conductor 122 of
shield 112 with a conductor 254 between the hubs of each loop 102A
and 102B. As another example, the number of spokes of a ground path
may be varied as shown by ground path 262 in FIG. 3D where,
compared to shield 212 in FIG. 3B, selected spokes 220 of shield
212 have been omitted.
[0046] In other embodiments, variations of shields 112 and 212 may
be used with differential inductors with a multi-turn format (not
shown) instead of the single loop inductors 102 and 202 in the
above embodiments.
[0047] FIG. 4 is a circuit diagram illustrating one embodiment of
controlled oscillator 280. As noted above, controlled oscillator
280 includes varactor 284, resistor 286 that represents the lossy
component from inductor 100 or 200, varactor 284, etc., and
amplifier 288 in parallel with either shielded differential
inductor 100 or shielded differential inductor 200. Connecting bars
142 and 144 are included for embodiments with shielded differential
inductor 100 to form at least a portion of the parallel
connections, and connecting bars 242 and 244 are included for
embodiments with shielded differential inductor 200 to form at
least a portion of the parallel connections.
[0048] Controlled oscillator 280 oscillates at frequencies
determined by the combination of inductance and capacitance
provided by inductor 100 or 200 and varactor 284 (i.e., an LC
tank), respectively. Amplifier 288 provides power to sustain the
oscillations. The frequency of controlled oscillator may be
controlled by adjusting a voltage provided to varactor 284 to
adjust the capacitance of varactor 284 in one embodiment.
[0049] Inductors 100 and 200 may be used with respect to a wide
variety of communications systems. FIG. 5 is a block diagram
illustrating one embodiment of selected portions of a low
intermediate frequency (low-IF) receiver 300 with an inductor 100
or 200 in a controlled oscillator 280. Receiver 300 includes a low
noise amplifier (LNA) 302, a mixer 304, low intermediate frequency
(IF) filter circuitry 306, processing circuitry 310, output
circuitry 312, local oscillator generation circuitry 322 with
controlled oscillator 280, and clock circuitry 324.
[0050] Receiver 300 is configured to receive a radio-frequency (RF)
signal (RF.sub.IN) and process the RF signal to generate a digital
audio and/or video media output 340 and/or an analog audio and/or
video media output 342. Receiver 300 forms an integrated
terrestrial or cable broadcast receiver configured to receive RF
signals. As used herein, an RF signal means an electrical signal
conveying useful information and having a frequency from about 3
kilohertz (kHz) to thousands of gigahertz (GHz), regardless of the
medium through which the signal is conveyed. Thus, an RF signal may
be transmitted through air, free space, coaxial cable, and/or fiber
optic cable, for example. Accordingly, receiver 300 may receive the
RF signal from a wired or wireless medium. In other embodiments,
receiver 300 may be configured to receive signals in another
suitable frequency range.
[0051] LNA 302 receives the RF signal and generates an amplified
output signal. The output of LNA 102 is then applied to mixer 304,
and mixer 304 generates real (I) and imaginary (Q) output signals,
as represented by signals 330. To generate low-IF signals 330,
mixer 304 uses phase shifted local oscillator (LO) mixing signals
328. LO generation circuitry 322 includes controlled oscillator 280
(shown in FIG. 4) and outputs two out-of-phase LO mixing signals
328 generated, in part, by inductor 100 or 200 and provided to
mixer 304. The outputs of mixer 304 are at a low-IF which may be
fixed or designed to vary, for example, if discrete step tuning is
used for LO generation circuitry 322. LO generation circuitry 322
also provides a reference signal to clock circuitry 324. Clock
circuitry 324 generates a clock signal from the reference signal
and provides the clock signal to processing circuitry 310. Low-IF
filter circuitry 306 receives the real (I) and imaginary (Q)
signals 330 and outputs real and imaginary digital signals, as
represented by signals 332. Low-IF filter circuitry 306 provides,
in part, signal gain, signal filtering, and analog to digital
conversion functions. Mixer 304 mixes the target channel within the
input signal spectrum down to an IF. The IF may be fixed at a
particular frequency or may vary within a low-IF ranges of
frequencies, depending upon the LO generation circuitry utilized
and how it is controlled. Low-IF filter circuitry 306 converts the
real (I) and imaginary (Q) signals to a baseband signal in the
digital domain and provides digital real (I) and imaginary (Q)
baseband signals 332 to processing circuitry 310.
[0052] Processing circuitry 310 performs digital filtering and
digital signal processing to further tune and extract the signal
information from digital signals 332. Processing circuitry 310
produces baseband digital media signals 336. When the input signals
relate to analog television broadcasts, the digital processing
provided by processing circuitry 310 may include, for example,
analog television demodulation. Processing circuitry 310 provides
baseband digital media signals 336 to output circuitry 312.
[0053] Output circuitry 312 outputs baseband digital media signals
336 as digital media output signals 340 in any suitable digital
format such as an IF I/Q format (e.g., low-IF (LIF) or zero-IF
(ZIF) I/Q). Output circuitry 312 may also convert the digital
baseband digital media signals 336 into analog media output signals
342 in any suitable analog format such as composite video baseband
signal (CVBS) and/or sound IF/audio frequency (SIF/AF).
[0054] FIG. 6 is a block diagram illustrating one embodiment of a
media system 400 that includes communications device 300 with
inductor 100 or 200 in controlled oscillator 280 as shown in FIG.
5. Media system 400 may be any type of portable or non-portable
system configured to provide a media output such as a mobile or
cellular telephone, a personal digital assistant (PDA), an audio
and/or video player (e.g., an MP3 or DVD player), and a notebook or
laptop computer.
[0055] Media system 400 includes communications device 300 that
receives a media transmission from an antenna 402 or other suitable
input and provides a digital and/or analog media signal to a
processing unit 404. Processing unit 404 performs any suitable
processing on the media signal (e.g., television demodulation on a
digital baseband signal) and provides the processed signal to a
media output unit 406 for output to a user. Processing unit 404 may
be omitted in some embodiments such that the media signal from
communications device 300 may be provided directly to media output
unit 406 in these embodiments. Media output unit 406 may include
any suitable type and/or combination of audio and/or video output
devices such as a television, a monitor, a display screen, a
speaker, or headphones.
[0056] An input/output unit 408 receives inputs from a user and
provides the inputs to communications device 300, processing unit
404, and/or media output device 406. Input/output unit 408 also
receives outputs from communications device 300, processing unit
404, and/or media output device 406 and provides the outputs to a
user. The inputs and outputs may include voice and/or data
communications, audio, video, image, and/or other graphical
information. Input/output unit 408 includes any number and types of
input and/or output devices to allow a user provide inputs to and
receive outputs from media system 400. Examples of input and output
devices include a microphone, a speaker, a keypad, a pointing or
selecting device, and a display device.
[0057] In the above embodiments, a variety of circuit and process
technologies and materials may be used to implement the
circuitries, devices, and systems. Examples of such technologies
include metal oxide semiconductor (MOS), p-type MOS (PMOS), n-type
MOS (NMOS), complementary MOS (CMOS), silicon-germanium (SiGe),
gallium-arsenide (GaAs), silicon-on-insulator (SOI), bipolar
junction transistors (BJTs), and a combination of BJTs and CMOS
(BiCMOS).
[0058] Although specific embodiments have been illustrated and
described herein, it will be appreciated by those of ordinary skill
in the art that a variety of alternate and/or equivalent
implementations may be substituted for the specific embodiments
shown and described without departing from the scope of the present
invention. This application is intended to cover any adaptations or
variations of the specific embodiments discussed herein. Therefore,
it is intended that this invention be limited only by the claims
and the equivalents thereof.
* * * * *